The unexpected closure of the I-40 bridge on May 11, 2021 prompted an FHWA memo mandating State DOTs to verify the integrity of butt welds on Non-redundant Steel Tension Members (NSTMs) fabricated from ASTM A514/A517 (T-1) 100 ksi steel using Non-Destructive Testing (NDT). This presented a significant challenge for Caltrans, given their substantial inventory of T-1 steel bridges constructed during the affected period. In response, Caltrans implemented a multi-layered inspection and oversight process, through several director's orders and emergency A&E Independent Quality Assurance (IQA) contracts. This presentation will detail the innovative inspection and remediation strategies employed for bridges throughout California, including:
• Formation of a T-1 steel advisory council to foster cross-functional collaboration.
• Development of risk register to identify top risks, set priorities and executive management support
• Development of a prequalification program to ensure Level II technician proficiency for these unique and complex inspections.
• Identification and documentation of internal redundancies to mitigate risk and avoid unnecessary inspections and repairs.
• Application of phased array ultrasonics for improved positioning and sizing of rejectable indications, enabling more precise mitigation.
• Use of microscopic evaluations to validate UT results and inform a data-driven inspection strategy that reduced inspection layers.
• Use of microscopy to separate rejectable indications due to stringers within base metals and avoiding unnecessary drilling
• Implementation of eddy current testing to detect welds through thick paint without removal
• Standardized report expectations and development of an automated report generation and tracking tool
The team will share these innovations and best practices, demonstrating their potential applicability beyond T-1 steel inspections.